CHAPTER III. METALLURGY AND PROPERTIES OF MATERIALS. IT will be well, so as to avoid repetition in succeeding chapters, to digress somewhat, in order to consider the" properties, and to some extent the metallurgy of the materials used in mechanical engineering, omitting only the consideration of their strength, which will be treated of in the second part of this work. These materials may be classified as follows:- — 1. Cast Iron. 2. Wrought Iron. 3. Cast Steel. 4. Forged Steel, 5. Copper. 6. Zinc. 7. Tin. 8. Gun Metal. 9. Brass. TO. Phosphor Bronze. IT. Muntz Metal. 12. Manganese Bronze. 13. White Metal. 14. Wood.* But we must first become acquainted with such chemical elements as are necessary to understand the processes we intend to consider. Such are: Carbon (C), Silicon (Si), Iron (Fe), Sulphur (S), Phosphorus (P), Manganese (Mn), and Oxygen (O). Carbon is an allotropic element, that is, it exists under different forms, which are: Charcoal, blacklead, and diamond. The first is pure carbon, and so is coke, or nearly so. The second is not lead^ and is also called graphite and plumbago \ and the third is the crystalline form. If carbon is allowed to unite with oxygen it forms carbon dioxide (COa), a gas. Carbonic oxide, or Carbon monoxide (CO), is another gaseous combination of carbon and oxygen. A chemical combination is the union of elements in such a way that they can only be separated by chemical action, while a mechanical mixture requires only mechanical means (very often filtration) to break it up. * For further materials see Appendix II,, pp. 794-801.